Pheophorbide-a conjugates with cancer-targeting moieties for targeted photodynamic cancer therapy

Pheophorbide-a, a non-selective photosensitizer, was conjugated with cancer-targeting moieties, such as folic acid, the CRGDLASLC peptide, the cRGDfK peptide and leuprorelin, for the purpose of targeted photodynamic cancer therapy. The cellular uptake of pheophorbide-a conjugates in cancer cells overexpressing the corresponding receptors of the targeting moieties was largely enhanced compared with that in the receptor-negative cells. In the study of in vitro photodynamic activity and selectivity of pheophorbide-a conjugates in the receptor-positive and receptor-negative cells, a pheophorbide-a conjugate, (14) with an αvβ6 ligand (CRGDLASLC) exhibited the highest selectivity in the positive FaDu cells. Targeted PDT with 14 induced cell death through apoptosis and morphological apoptosis-like characteristics. These results suggest that pheophorbide-a conjugate 14 could be utilized in selective photodynamic therapy for oral cancers primarily expressing the αvβ6 receptor.